Inverse of block triangular matrix

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How to find the pseudo-inverse of the following block lower triangular matrix? $$X=\begin{bmatrix} A & 0 \\ c & d \\ \end{bmatrix}$$ Where $A$ is a $n\times n$ lower triangular matrix, $d$ is a scalar and $c$ is a $1\times n$ vector. Suppose that I know inverse of $A$ a priori.